filip62/armv8a-call-java-method-from-assembly

This demonstrates how to write a native library with a procedure calling a Java method, defined in an Android app that previously invoked that native procedure. The library is written in ARMv8-A assembly.

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About

This example demonstrates how to :

• assemble a library written with the ARMv8-A 64 bits GNU ASsembly syntax
• call a native procedure, included in this library, from an Android app using the JNI.

The called procedure will then call back a Java method, defined in the Android Application, using the JNI helpers.

Building

Building using GNU Make

Requirements

• GNU AS (aarch64)
• Gold linker (aarch64)
• An ARMv8-A 64 bits Android phone/emulator on which you have installation privileges

Build

Run make from this folder

Manually

Run the following commands :

# cross compiler prefix. Remove if you're assembling from an ARM machine
export PREFIX="aarch64-linux-gnu"
export APP_DIR="./apk"
export LIBNAME="libarcane.so"
${PREFIX}-as -o decypherArcane.o decypherArcane.s
${PREFIX}-ld.gold -shared --dynamic-linker=/system/bin/linker -shared --hash-style=sysv -o $LIBNAME decypherArcane.o
mkdir -p $APP_DIR/app/src/main/jniLibs/arm64-v8a
cp $LIBNAME $APP_DIR/app/src/main/jniLibs/arm64-v8a

Building using Android ndk-build

Requirements

• The Android NDK path in your system's PATH directory

Build

• On Windows, run 'mkbuild.bat'
• On Linux, run 'mkbuild.sh'

Installing the prepared APK

• Connect your ARMv8-A 64 bits Android phone/emulator
• open a shell or a "command window"
• cd to the apk folder

Then :

• On Windows run gradlew installDebug.
• On Linux run ./gradlew installDebug